The present disclosure is related to manufacture technique for integrated silicon photonics device, and particularly to a vertically integrated hybrid waveguide with accurate interlayer thickness control and a method of making the same.
As science and technology are developed rapidly, processing speed and capacity of the computer increase correspondingly. The information transmission or reception using the traditional cable is limited to lower bandwidth as compared to what optical fiber provides. In the advent of Information Age, traditional electrical communication has been largely replaced by fiber-optic communication which provides much higher bandwidth and much longer distance transmission. An optical communication system includes both electrical devices and optical devices, devices for converting electrical signal and optical signal back and forth, and devices for processing these signals. With the advances of optical communication technology and applications driven by the market demand on increasing bandwidth and decreasing package footprint, more intensive effort and progress have been seen in the development of electro-photonic integrated circuits on silicon-on-insulator (SOI) substrate for forming those communication devices.
For example, SOI-based silicon photonics device containing Si waveguide can monolithically be integrated with optically active devices such as electro-optic modulators and Ge photo-detectors (PD). Due to high refractive index contrast of Si vs. SiO2, it enables manufacturing of densely integrated electronic-photonic components at low costs and high volumes. Another advantage lies in good thermal conductivity of Si, which makes it suitable to fabricate thermally tunable photonic devices. However, for improving the performance with high tolerance on environmental temperature, susceptible to higher optical power, high optical transparency, lower propagation loss, less dispersion, and less sensitivity to waveguide shape, different material such as Si3N4 is introduced into Si-based SOI photonics platform to enjoy both advantages to Si and Si3N4 waveguide. It is desirable to have improved technique to integrate both active and passive optical functionalities in a same photonics chip. The hybrid waveguide which is made on a Si3N4-on-SOI platform is a good candidate to design and fabricate good performance of both passive and active optical devices.